A nuclear reactor can load-follow (increase or decrease their output) by up to 5% of their rated capacity per minute in normal operation: https://snetp.eu/wp-content/uploads/2020/05/SNETP-Factsheet-...

For power plants, this is glacial. A power grid has to balanced perfectly on a sub-second level. Also, you can only do this down to about 50% of rated capacity. Below that you have to switch it off completely.

If you combine this with renewable generation, it all falls apart. A cloud passing over a large PV installation will drop generation much faster than nuclear plants will ever be able to follow (by increasing generation). So if you want to have a substantial share of renewable generation (which, remember, is the cheap stuff), you can't have more than a token nuclear capacity, because you need to invest the money you might want to spend on nuclear on battery and hydro storage.

The other aspect is the economics of nuclear itself. Nuclear power plants are the most capital intensive generation capacity you can build. Even when driving them at the maximum of their rated capacity, the have a levelized cost of electricity several times that of PV and Wind per kwh. Requiring routine load following for nuclear would basically guarantee that no one ever builds a nuclear reactor again.

There are reasons to build new nuclear, but it's not cheap/reliable power generation. You build it to have access to a nuclear industrial base, as well as the research and professional community to run a military nuclear program. Or you actually succeed in creating a Small Modular Reactor, which might be suitable for niche applications (i.e. power isolated communities in extreme remote locations). Or you are simply fascinated by the technology and want to invest a ton of money on the off chance that it will produce some unforeseen technological breakthrough (though arguably you'd do better with investing in nuclear fusion from my limited understanding of the research).

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robocat 3 days ago | parent [-]

> If you combine this with renewable generation, it all falls apart

Rubbish. Only true if the renewable generation is poorly integrated. Solar plus batteries can provide synthetic inertia if the incentives/regulations are correctly designed.

Australia has been adding oodles of solar, and they have been doing it surprisingly well.

Nuclear can load follow, within limitations: https://news.ycombinator.com/item?id=36254716

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tfourb 3 days ago | parent [-]

> Solar plus batteries can provide synthetic inertia if the incentives/regulations are correctly designed.

Yes, but why build nuclear at all, if you are already building PV + batteries? Nuclear is much more expensive than that combination. And if you add nuclear capacity on a level that actually matters (i.e. 30%+ of peak load), you run into real integration problems.

As I've written elsewhere, a toke nuclear program can make sense if you want to keep the industrial base, institutional knowledge and expertise around, i.e. to guarantee independent access to nuclear weapons. But it is ludicrous to make nuclear a cornerstone of your energy policy. Not even China is expanding its share of nuclear in total energy generation. They keep it around as a strategic asset, but a subsidized one.

For countries like Denmark and Spain I'd be pulling my hair out if my government would start throwing money into the money pit that is nuclear power (and it is inevitably is government money, because no nuclear power plant has ever been built without government subsidies and/or price guarantees).

> Nuclear can load follow, within limitations

Yes, but it makes zero economic sense to do so. Nuclear is multiple times more expensive per kwh than PV + batteries, even if you run it at max capacity continuously. If you require nuclear to load follow on a regular basis, not a single reactor will ever be built again.

	▲	robocat 3 days ago \| parent [-]
		> Yes, but why build nuclear at all I wasn't suggesting that. Why did you assume that and then argue against something I didn't say?